spawn down: reports force-kill for agents that exit gracefully

[laynepenney]

Bug

gr spawn down --agent <name> reports "force-killed (did not exit within 10s)" even when the agent exits cleanly after receiving /exit.

Root cause

Two issues:

1. Default timeout too short (10s)

Claude Code's /exit runs hooks (precompact, journal writes, session save) that can take 10-15s on an M2 Air. The polling loop expires while the agent is still gracefully shutting down.

Fix: Increase default from 10s to 30s.

2. Stale state in Phase 3

Phase 3 reports from the Phase 2 states[i] vector without re-checking. If the agent exits between the polling deadline and the kill-window call, it's reported as "force-killed" based on stale state.

Fix: For agents that timed out in Phase 2, do one final pane_exit_state() check before kill-window:

let final_state = if states[i] == PaneState::Running {
    match pane_exit_state(session, name) {
        Some(true) => PaneState::Exited,
        _ => PaneState::Running,
    }
} else {
    states[i]
};
// Then kill-window, then report using final_state

Impact

Cosmetic only. Agents do exit cleanly; the output is misleading.

Location

src/cli/commands/spawn.rs lines 532-534 (timeout default), 620-680 (polling + reporting)